Python Network Programming Cheat Sheet – Downloadable JPG & PDF

All the tables provided in the cheat sheets are also presented in tables below which are easy to copy and paste.

The Python Network Programming Cheat Sheet covers:

• Required common installation modules: PIP and IDLE
• Top python network programming libraries
• Network forensics: Required python libraries and scripts
• Python Keywords
• Data Types, Math operators
• Network Analysis with Python
• The dnspython library
• Socket Module (Berkley API interface)
• Socket Types, Creating Sockets
• Socket Examples
• Script Examples
• Parsing Modules

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What’s included in this cheat sheet

The following categories and items have been included in the cheat sheet:

Required common installation modules: PIP and IDLE

PIP (Python Package Installer)

$ sudo apt-get install python-pip

IDLE (Integrated Development and Learning Environment)

$ sudo apt-get install idle

Top python network programming libraries

Django

High-level Python Web framework for rapid development and pragmatic

pycos (formerly asyncoro)

Python framework for asynchronous, concurrent, network, distributed programming and distributed computing

Diesel

A clean API for writing network clients and servers. TCP and UDP supported. Bundles clients for HTTP, DNS, Redis, Riak and MongoDB.

Pulsar

Easy way to build scalable network programs

Twisted

Event-based framework for internet applications: HTTP clients and servers, SSHv2 and Telnet, IRC, XMPP, IMAPv4, POP3, SMTP, IMAPv4, POP3, SMTP, etc.

NAPALM

Network Automation and Programmability Abstraction Layer with Multivendor support – For dealing with dvice vendors

gevent

A coroutine -based Python networking library that uses greenlet to provide a high-level synchronous API on top of the libev or libuv event loop

Celery

Asynchronous task queue/job queue based on distributed message passing

Network forensics: Required python libraries and scripts

EDDIE Tool

System and network monitoring, security, and performance analysis agent for python

pypcap

Small packet capture tool based on python and pcap

Paramiko

Implementation of the SSHv2 protocol, providing both client and server functionality

pip

Package installer for python

The Python Package Index (PyPI)

Repository of software for the Python

Python Keywords

>>> import keyword

>>> print(keyword.kwlist)

Python 2.7.15+ [‘and’, ‘as’, ‘assert’, ‘break’, ‘class’, ‘continue’, ‘def’, ‘del’, ‘elif’, ‘else’, ‘except’, ‘exec’, ‘finally’, ‘for’, ‘from’, ‘global’, ‘if’, ‘import’, ‘in’, ‘is’, ‘lambda’, ‘not’, ‘or’, ‘pass’, ‘print’, ‘raise’, ‘return’, ‘try’, ‘while’, ‘with’, ‘yield’]

Python 3.8.0 [‘False’, ‘None’, ‘True’, ‘and’, ‘as’, ‘assert’, ‘async’, ‘await’, ‘break’, ‘class’, ‘continue’, ‘def’, ‘del’, ‘elif’, ‘else’, ‘except’, ‘finally’, ‘for’, ‘from’, ‘global’, ‘if’, ‘import’, ‘in’, ‘is’, ‘lambda’, ‘nonlocal’, ‘not’, ‘or’, ‘pass’, ‘raise’, ‘return’, ‘try’, ‘while’, ‘with’, ‘yield’]

Data Types

Text

str – x = “Hello World”

Numeric

int, float, complex

Sequence

list, tuple, range

Mapping

dict

Set

set, frozenset

Boolean

bool

Binary

bytes, bytearray, memoryview

Math operators

**

Exponent 4 ** 2 = 16

%

Modulus/Remainder 43 % 5 = 3

//

Integer division 11 // 5 = 2

/

Division 11 / 5 = 2.2

*

Multiplication 3 * 3 = 9

–

Subtraction 8 – 3 = 5

+

Addition 2 + 2 = 4

==

Equal to

!=

Not equal to

<

Less than

>

Greater Than

<=

Less than or Equal to

>=

Greater than or Equal to

Comments

#

Can be used at the start of a line, or from within a line to the end of the line

Network Analysis with Python

Use NMAP with port scanner

$ pip install python-nmap

Commands to run NMAP scan

import nmap

nmScan = nmap.PortScanner()

nmScan.scan('10.1.0.0', '25-443')

NMAP commands used with python

nmScan.scaninfo() # {'tcp': {'services': ‘25-80’, 'method': 'connect'}}

nmScan.all_hosts()

nmScan['10.1.0.0'].hostname()

nmScan['10.1.0.0'].state()

nmScan['10.1.0.0'].all_protocols()

nmScan['10.1.0.0']['tcp'].keys() # Results -[80, 25, 22, 135]

nmScan['10.1.0.0'].has_tcp(25) # Result True/False

nmScan['10.1.0.0'].has_tcp(21) # Result False/True

The dnspython library

Installation

$ pip install dnspython

Basic DNS query

import dns.resolver

name = 'google.com'

for qtype in 'A', 'AAAA', 'MX', 'NS', 'TXT', 'SOA':

answer = dns.resolver.query(name,qtype, raise_on_no_answer=False)

if answer.rrset is not None:

print(answer.rrset)

Get MX target and name preference

import dns.resolver




answers = dns.resolver.query('dnspython.org', 'MX')

for rdata in answers:

print ('Host', rdata.exchange, 'has preference', rdata.preference)

Socket Module (Berkley API interface)

Primary Functions an Methods

socket() • ind() • listen() • accept() • connect() • connect_ex() • send() • recv() • close()

Socket Types

SOCK_STREAM

For TCP protocols • Reliable transmission • Packet sequence • Connection-oriented • Bidirectional

SOCK_DGRAM

For UDP protocols • Unreliable transmission • No sequence of packets • Connectionless(UDP) • Not Bidirectional

Creating Sockets

import socket # Imports the socket method

socket.socket() # Function that creates socket

sock = socket. socket (socket family, socket type, protocol=value)

Socket Family

AF_UNIX or AF_INET

Socket Type

SOCK_STREAM or SOCK_DGRAM for TCP & UDP respectively

• e.g. TCP – UDP2 = socket. socket (socket.AF_INET, socket.SOCK_DGRAM)

• e.g. UDP – TCP2 = socket. socket (socket.AF_INET, socket.SOCK_STREAM)

Client socket method

connect()

Server socket method

bind() • listen(backlog) • accept()

TCP socket methods

s.recv() # Receive TCP packets

s.send() #Send TCP packets

UDP socket methods

s.recvfrom() # Receives UDP packets

s.sendto() # Transmits UDP packets

More Socket Methods

close()

Close the socket connection

gethostname()

Returns a string which includes the hostname of the current PC

gethostbyname()

Returns a string which includes the hostname and IP address of the current PC

listen()

Setup and start TCP listener

bind()

Attach (host-name, port number) to the socket

accept()

TCP client connection wait

connect()

Initiate TCP server connection

TCP Socket Methods

mysocket.accept()

Returns a tuple with the remote address that has connected

mysocket.bind( address )

Attach the specified local address to the socket

mysocket.connect( address )

Data sent through the socket assigns to the given remote address

mysocket.getpeername()

Returns the remote address where the socket is connected

mysocket.getsockname()

Returns the address of the socket’s own local endpoint

mysocket.sendto(data, address)

Force a data packet to a specific remote address

Socket Blocking

setblocking(1)

Setup block

setblocking(0)

Remove / un-setup block

Get port number using domain name

import socket

socket.getservbyname('domain name')

Check support for IPV6

import socket

socket.has_ipv6 # Answer is TRUE or FALSE

getaddrinfo() – Bind Server to a Port

from socket import getaddrinfo

getaddrinfo(None, 'FTP', 0, socket.SOCK_STREAM, 0, socket.AI_PASSIVE)

[(2, 1, 6, '', ('0.0.0.0', 21)), (10, 1, 6, '', ('::', 21, 0, 0))]

Socket Examples

Client-side socket example

import socket

s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)

host=socket.gethostname()

port=1111

myserver.bind((host,port)) # replace myserver and myclient with repsctive IPs

myserver.listen(5)

while True:

myclient,addr=myserver.accept()

print("Connected to {str(addr)}")

myclient.send(msg.encode("ascii"))

myclient.close()

Client-side Socket example with Comments

# import the socket library

import socket




# create a socket object

s = socket.socket()

print ("Socket created")




# reserve a port on the computer which can be anything

port = 1111




# bind to the port

# empty string in the IP field instead of an IP makes server listen to requests

# coming from other computers on the network

s.bind(('', port))

print ("socket binded to %s" %(port))




# make socket into listening mode

s.listen(5)

print ("socket is listening")




# loop until user interrupt it or an error occurs

while True:




# Establish connection with client.

c, addr = s.accept()

print ('Got connection from', addr)




# send a thank you message to the client.

c.send('Thank you for connection')




# Close the connection

c.close()

Script Examples

Create list of devices

>>>devices = ['SW1', 'SW2', 'SW3']

Create VLAN dictionary list

vlans = [{'id': '100', 'name': 'staff'}, {'id': '200', 'name': 'VOICE'},

{'id': '300', 'name': 'wireless'}]

Write functions to collect commands and push to the network

>>>def get_commands(vlan, name):

commands = []

commands.append('vlan ' + vlan)

commands.append('name ' + name)




return commands




>>> def push_commands(device, commands):

print('Connecting to device: ' + device)

for cmd in commands:

print('Sending command: ' + cmd)

Create VLANs in multiple switches using python script

>>>for vlan in vlans:

id = vlan.get('id')

name = vlan.get('name')

print('\n')

print('Configure VLAN:' + id)

commands = get_commands(id, name)

for device in devices:

push_commands(device, commands)

print('\n')

Citation: https://www.oreilly.com/library/view/network-programmability-and/9781491931240/ch04.html

Disable router interface using python command

>>> from push import push_commands

device = 'router2'

commands = ['interface Eth0/1', 'shutdown']

push_commands(device, commands)

Parsing Modules

argparse()

The argparse module makes it easy to write user-friendly command-line interfaces. The program defines what arguments it requires, and argparse will figure out how to parse those out of sys.argv

Creating a parser

>>> parser = argparse.ArgumentParser(description='Process some integers.')

Adding arguments

>>> parser.add_argument('integers', metavar='N', type=int, nargs='+',

... help='an integer for the accumulator')

>>> parser.add_argument('--sum', dest='accumulate', action='store_const',

... const=sum, default=max,

... help='sum the integers (default: find the max)')

Parsing arguments

>>> parser.parse_args(['--sum', '7', '-1', '42'])

Namespace(accumulate=, integers=[7, -1, 42])

Python network programming FAQs

How Python can be used in networking?

Python is a flexible programming language and it can be used to automate many business tasks. On networks, you would use Python scripts to perform maintenance tasks, collect and transform data, or to update settings. A useful application for Python on networks is to ensure coordination between different components in a system. For example, all of the elements in a software-defined network can be aligned through the use of Python scripts.

Is Python good for socket programming?

You can bind and release a socket with Python very easily. There are a number of network traffic management services that you can construct with Python, such as resequencing packets or checking for abandoned connections.

Why is Python good for network automation?

The short answer to why Python is good for network programming is that Cisco System uses it for the on-board programs on its devices, so if they put in lots of research into the relative benefits of programming languages for networking, you could just take their word for it and save yourself a lot of time. Pointing to the qualities that recommend Python for network programming is that it is extensible by libraries in the way that C is but it is much easier to read than C and it doesn’t need to be compiled.